Method and apparatus for abrasive recycling and waste separation system

ABSTRACT

The present invention provides a method of handling abrasive solids materials used in an abrasive cutting procedure which jets a high-pressure abrasive slurry through a nozzle ( 7 ) onto a work piece over and/or in a catcher tank ( 8 ). This handling method includes catching the used abrasive slurry together with work piece kerf material in the catcher tank, and passing at least some abrasive solids collected in the catcher tank as a slurry to a partitioning apparatus which includes a vibratory sieve ( 27 ). The handling method also includes partitioning the slurry with the partitioning apparatus in order to provide at least two solids streams. One of the solid streams passes through the sieve and the other passes across the sieve whilst entrained as a slurry. The handling method further includes passing as a slurry to the nozzle ( 7 ) for jetting a pressurised or pressurisable slurry that has partitioned solids stream which has passed through the sieve ( 27 ).

RELATED PATENT DATA

This application is a divisional of U.S. patent application Ser. No.10/500,418, filed Feb. 18, 2005, now U.S. Pat. No. 7,147,545, whichclaims priority to Patent Cooperation Treaty application Serial No.PCT/SG02/00296, which was filed Dec. 27, 2002, and which claims priorityto Singapore Application Serial No. 200108107-4, which was filed Dec.28, 2001.

The present invention relates to materials handling and moreparticularly to any one or more of a method of partitioning solids of aslurry three ways, partitioning apparatus useful therefor, a method ofhandling abrasive solids materials so as to provide for at least apartial recycle of part thereof, a related abrasive slurry cutting plantand abrasive material prepared by such procedures for subsequent use.

In a jet cutting procedure a water jet customarily employs abrasivesolids of a desirable size range, density, hardness and abrasiveness toenhance the erosion effect of the jet on a wide variety of work piecesthat normally are interposed between the nozzle from which the jetissues and a catcher tank. Examples of the abrasive type materials usedare aluminium oxide, garnet, copper slag, etc.

Examples of materials handling insofar as the abrasive components ofplant and procedures in water jet systems include those disclosed in the2000 publication of BHR Group entitled “Jetting Technology” pages 389 to399.

It can be seen that such prior art systems have attempted to re-employsome of the abrasive caught by the catcher tank along with kerf from thework piece whilst rejecting solids of an undesirably small particlesize. For this purpose one prior art procedure has employed both ahydro-cyclone and a sieve. Such hydro-cyclones are prone to wear with aresult in significant maintenance costs which detracts from the costsaving recycle. Such wear in addition reduces performance and requiresthe use of large quantities of water.

Another system disclosed uses sieve screens (see www.easijet.com).

The present invention is directed to methods and apparatus havingapplication in a partial recycle of abrasive materials used in a waterjet cutting system which relies on a flow through over a sieve toachieve a partition of particles in the flow through or on the sieve notto be used through the nozzle from those that are to be so used. Such aprocedure can remove oversized particles that might have a tendency toblock the jetting nozzle and at the same time can ensure there is littleuse in the recycle of abrasive material or kerf material of too small asize to be useful.

The system also optionally lends itself to a makeup of abrasivematerials in use throughout the overall system that does not underminethe value of the recycle procedure.

The handling system useful in such a jet cutting plant will haveapplication elsewhere wherever a partitioning of solids entrained in aslurry at least two (and preferably three) ways is required. Thereforethe partitioning apparatus and partitioning method of the presentinvention has wider applicability, eg; with any other liquid entrainmentsystem.

It is an object of the present invention to provide apparatus andmethods which meet at least some of the abovementioned criteria.

In a first aspect the present invention consists in a method of handlingabrasive solids materials used in an abrasive cutting procedure of akind which, in use, jets a high pressure abrasive slurry through anozzle onto a work piece over and/or in a catcher tank, the handlingmethod comprising or including

catching the used abrasive slurry together with work piece kerf materialin said catcher tank,

passing at least some of abrasive solids collected in the catcher tankas a slurry to a partitioning apparatus that includes a vibratory sieve,

partitioning with said partitioning apparatus the slurry to provide atleast two solids streams one of which passes through the sieve and oneof which passes across the sieve whilst still entrained as a slurry, and

passing as a slurry to the nozzle for jetting a pressurised orpressurisable slurry which includes partitioned solids stream that haspassed through the sieve.

As used herein “slurry” refers to any liquid vehicle (whatever pressure)associated with solids e.g. such that when moving the liquid entrainsthe solids.

Preferably there is a partitioning of the solids by the partitioningapparatus three ways, the aforementioned two solids streams andoversized solids that drop from the slurry that passes across the sieveand are at least initially retained on the sieve.

Preferably the solids passed to the nozzle are in the size range of from10% to 70% of nozzle diameter.

Preferably the passing as a slurry to the nozzle involves high pressurewater expression from a pressure vessel.

Preferably said partitioning apparatus comprises or includes

a housing having

-   -   a first inlet,    -   a first outlet, and    -   a collection zone or second outlet, and

a sieve disposed below said first inlet and said first outlet but abovesaid collection zone or second outlet,

and wherein said first inlet is to receive and pass the slurry at a rateand velocity into the housing above the sieve such that at least some ofthe liquid component(s) of the slurry will, as a flow through, entrainsmall and/or less dense solids out through said first outlet,

and wherein the rate and velocity of intake into the housing via thefirst inlet above the sieve and the outflow via the first outlet is suchas to enable at least some oversize solids to settle on the sieve (wherethey are of an appropriate density) and solids (not entrained out ofsaid first outlet) of sufficient density and of a size less than that ofthe oversized material to pass down through the sieve.

Preferably said sieve is a directly or indirectly shaken and/orvibratory sieve.

Preferably said partitioning apparatus has a collection zone and thereis a valved flow path therefrom to a pressure vessel from which, asrequired at the nozzle, high pressure water can express the solidsstream to pass to the nozzle.

Preferably there is controllable liquid and/or slurry flow path fromsaid pressure vessel back to said collection zone of the partitioningapparatus capable of moving as a slurry more solids from said collectionzone through, via the valved flow path, to said pressure vessel.

Preferably there is included the step of providing a makeup feed ofabrasive solids.

Preferably said makeup solids are introduced into said catcher tank.

Preferably there is provided a solids agitation water feed into thecatcher tank.

Preferably there is an overflow out take of at least water from thecatcher tank.

Preferably a control system reliant on at least one sensor provides acontrol of valves and pumps which determines the modes of operation ofthe system capable of performing the method.

In a second aspect the present invention consists in abrasive slurrycutting plant comprising or including an abrasive supply system,

a catcher tank,

a nozzle for jetting as a slurry abrasive solids onto any appropriatelypositioned work piece over and/or in the catcher tank,

partitioning apparatus,

apparatus on demand to provide a supply of high pressure water into saidpressure vessel with an ability to express water and/or a slurrytherefrom,

apparatus to convey as a slurry caught solids from the catcher tank tosaid partitioning apparatus,

apparatus to convey a useable abrasive solids stream as a slurry fromthe partitioning apparatus on demand to the pressurisable vessel,

(optionally) apparatus on demand to provide a water feed to the catchertank,

(optionally) apparatus to provide, as part of the apparatus to convey ausable abrasive solids stream, a feed of water for the solids stream topass from the partitioning apparatus to the pressure vessel,

Preferably there is provided apparatus to provide a makeup feed ofabrasive solids.

Preferably said makeup feed is a feed into said catcher tank.

Preferably the partitioning apparatus comprises or includes

a housing having

-   -   a first inlet,    -   a first outlet, and    -   a collection zone or second outlet, and

a sieve disposed below said first inlet and said first outlet but abovesaid collection zone or second outlet,

wherein said first inlet is to receive and pass a slurry received fromthe catcher tank at a rate and velocity into the housing above the sievesuch that at least some of the liquid component(s) of the slurry will,as a flow through, entrain a first part of the solids out through saidfirst outlet,

and wherein the rate and velocity of intake of the slurry into thehousing via the first inlet above the sieve and the outflow via thefirst outlet is such as to enable at least some oversize material tosettle on the sieve and at least some sieve passable solids of greaterdensity than the entrained solids of the flow through to pass downthrough the sieve.

Preferably there is a said collection zone which is a reservoir fromwhich the collected solids as a slurry on demand (optionally with theaddition of additional water) can be fed as a slurry to said pressurevessel from whence the solids may be expressed to the nozzle under theaction of high pressure water passing into such pressure vessel.

Preferably apparatus is included whereby said sieve, in use, vibratesand/or shakes.

In still a further aspect the present invention consists in partitioningapparatus capable of partitioning the solids of a slurry at least threeways, said apparatus comprising or including

a housing having

-   -   a first inlet,    -   a first outlet, and    -   a collection zone or second outlet, and

a sieve disposed below said first inlet and said first outlet but abovesaid collection zone or second outlet,

wherein said first inlet is to receive and pass a slurry received fromthe catcher tank at a rate and velocity into the housing above the sievesuch that at least some of the liquid component(s) of the slurry will,as a flow through, entrain a first part of the solids out through saidfirst outlet,

and wherein the rate and velocity of intake of the slurry into thehousing via the first inlet above the sieve and the outflow via thefirst outlet is such as to enable at least some oversize material tosettle on the sieve and at least some sieve passable solids of greaterdensity than the entrained solids of the flow through to pass downthrough the sieve.

Preferably there is provided a drive whereby said sieve, in use, iscapable of being actively shaken and/or vibrated and, in use, oversizematerial that settles on the sieve may migrate therefrom to an optionaltrap for such material.

Preferably said collection zone is a reservoir adapted so that collectedsolids as a slurry on demand (optionally with the addition of additionalwater) can be fed as a slurry to a pressure vessel.

In yet a further aspect the present invention consists in a method ofpartitioning solids of a slurry three ways, said method comprising

providing a housing having an inlet, a first outlet, and a second outletor collection zone, and, disposed therein, a sieve disposed below saidfirst inlet and said first outlet but above said second outlet orcollection zone,

passing a slurry via said inlet into the housing across the sieve and,in part, out of said first outlet whilst at least some of the solids ofthe slurry fall onto and/or through the sieve,

harvesting or using the solids that have passed through said sieve andout of said second outlet or into said collection zone,

harvesting or removing those solids collected on the sieve, and

harvesting or disposing of those solids that have passed out of saidfirst outlet.

Preferably the harvesting or using of the solids that pass out of saidsecond outlet or into said collection zone is as a slurry.

Preferably the harvesting or disposal of the solids that pass out ofsaid first outlet is as a slurry.

Preferably the harvesting or using of the solids that pass through thesieve is by a slurry feed thereof from said collection zone or from saidsecond outlet into a pressure vessel from whence the solids may beexpressed under the action of water addition into such pressure vessel.

In still a further aspect the present invention consists in abrasivematerials in a water slurry for use in a jet cutting procedure preparedfor such use using an at least partial recycle procedure reliant on amethod of the present invention.

A preferred form of the present invention will now be described withreference to the accompanying drawings in which,

FIG. 1 is a diagrammatic view showing a slurry jet issuing nozzle over acatcher tank from whence a fluid tight flow path exists to an inlet intopartitioning apparatus having disposed within a housing thereof a sieveover a collection zone and under an outlet for flow through of part ofthe slurry above the sieve,

FIG. 2 is a diagrammatic view of a whole abrasive jet cutting plantemploying the arrangement substantially as disclosed in FIG. 1 showingappropriate controls, and

FIG. 3 shows a preferred housing with sieve of a partitioning plant incutaway perspective.

In the preferred form of the present invention a nozzle 7 is adapted toreceive a slurry containing abrasive materials (preferably in a sizerange of from about 10% to about 70% of the nozzle diameter via a flowpath 21 from a pressure vessel 17. The abrasive slurry from the nozzle 7is jetted downwardly over the catcher tank 8.

The catcher tank 8 includes an isolation valve 9 capable of isolatingthe tank from the drain via flow path 38. There is a flow path 22 to aninlet 23 of the partitioning apparatus such as preferably disclosed inFIGS. 1 and 3. This flow path 22 includes a further catcher tankisolation valve 10.

The partitioning apparatus comprises a hopper 25 having an inlet 23 andan outlet 26 both above a sieve screen 27 capable of being shaken orvibrated actively above an outlet (the second outlet) 28 which leads toa collection zone 15.

The first outlet 26 forms part of a flow path 29 via a valve 29 to adrain or catchment.

The collection zone 15 includes a flow path therefrom 32 to the pressurevessel 17. That flow patch 32 is preferably valved by valve 16.

A low pressure water supply (for example 6 to 9 bar) 19 passes via aflow path 33, a pump 31, and a flow path 34 into the pressure vessel 17.As a consequence of use of pump 31 a high pressure water feed (forexample, of from 690 to 1000 bar) which is sufficient pressure (when thevalve 16 is closed and suction pump 12 is not operating on the flow path35 back to the partitioning apparatus) to express an abrasive materialladen slurry from tank 17 via the flow path 36 through the nozzle 7 as ajet.

The water supply 19 is capable of being introduced at valve 16 (eg; anelectrical solenoid valve) into the flow path 32 as shown in FIG. 2.

A water and/or slurry return from pressure vessel 17 under the action ofa vacuum pump 12 on flow path 35 into the catcher assists in providingthe water requirements for a slurry best able to flow along the flowpath 32 to the pressure vessel 17.

A air pressurising fan or pump 1 on a flow path 40 into make up tank 2can force, when valve 5 allows and valve 3 is closed, make up abrasiveinto the catcher tank 8 via flow path 39 and, when valve 5 is closed andvalve 3 is open, to the drain 37.

A drain is depicted generally as 37 and to this can be allowed to flowpart of the water feed from the pump 31, the outflow of the undersizeless dense materials from the partitioning apparatus (eg; under actionof vacuum pump 30) and any water and light material outflow from thecatcher tank 8 (via the flow path 38). In addition, if desired a make upabrasive material tank 2 can itself have an operable a feeder valve 5 tothe catcher tank 8 where it blends make up feeds of abrasive with usedabrasive (and kerf material from any work piece interposed between theslurry and the jet issuing nozzle 7).

A control panel 4 is electrically connected to at least valve 5,(optionally) valve 6, valve 10, valve 16, (optionally) vacuum pump 30,(optionally) pump 31, (optionally) pump 12, (optionally) air supply fan1.

In operation the slurry passes thru nozzle 7 and cuts workpiece. Thespent abrasive and workpiece waste falls into catch tank 8 below. Theslurry pump 11 sucks the slurry from the catch tank 8 thru the sieveshaker 13. The small light particles of product waste and non-recyclableabrasive follows the flow out of the sieve shaker 13 to the slurry pump11 and off to waste containment. The heavier and larger (recyclable)abrasive particles drop onto the sieve screen in the shaker. Any largescrap particles too big to pass thru the screen remains on top forcollection, the remaining particles pass thru the screen and fill thehopper below. An abrasive height measurement device 14 inside the hoppersends a signal to the new abrasive feed valve 5 to add new abrasive intothe catch tank when the level in the hopper 15 falls below a certainpoint. The new abrasive feed valve is fed with abrasive from theabrasive hopper 2 under pressure of air and feeds abrasive into the mixto replace the volume of abrasive that has passed straight thru thesieve shaker 13 to the slurry pump 11 and waste due to it being too fineto be recycled. This new abrasive mixes with the used slurry in thecatch tank 15 and also passes together with it thru the sieve shakerremoving any oversized abrasive.

When the pressure vessel 17 needs to refill itself another suction pump12 sucks water from the vessel and creates a vacuum which then drawsabrasive laden slurry from the hopper 15 into the vessel 17. The heavyabrasive settles into and fills the vessel whilst the rest of the waterpasses thru the slurry pump 12 and is pumped back into the sieve shaker.

A preferred form will now be described with reference to the FIG. 3.

FIG. 3 shows in cross section the inlet 23 being a 15 mm diameter inletand the outlet 26 as a 15 mm diameter outlet both positioned about 100mm above the sieve 27 which in one form of the present invention is a150 U.S. mesh standard sieve adapted to allow through particles below0.15 mm in size with such a sieve and such inlet/outlet configurationpreferably distance across the housing 25 between the first inlet orinlet 23 and the first outlet 26 is approximately 250 mm.

We have determined that where a slurry having abrasive materials andkerf therein with a solids content of 0.3 kg/min at a flow rate of 2liters/min is introduced by the inlet 23 there is, in steady stateconditions, an outflow of about 2 liters/min via the outlet 26 with theoutcome that most of the oversized materials, (ie; above 0.15 mm inparticle size of sufficient density) are collected on the screen 27carried under a removable assembly 28 (the removal of preferably alsoremoves an optional trap 29 to which above 0.15 mm particles migrateunder the effect of flow and vibration) and most of the other particlessizes (ie; below 0.025 mm particle size) exit via the outlet 26 whilstthe remainder settles into the collection zone 15 from whence it can bereused.

That proportion of material wrongly passing through to the outlet 26,(ie; is material that should have reached collection zone 15) is notgreater than about 5% w/w and that material that should have passed outof the outlet 26 (ie; undesirable lighter or smaller abrasive particles)but which is collected in collection zone 15 is no more than about 5%w/w.

It has been found that the three way partitioning can be achieved by themethods and apparatus of the present invention for various slurries andvarious rates of flow thereof by appropriate tuning to geometry (e.g.inlet with respect to screen and outlet) and screen size.

It is appropriate to ensure with geometry of the apparatus and flowrates that the slurry transit times in flow through from inlet 23 tooutlet 26 is such that it is higher than the settling out time of thosesmall particles to be excluded from the collection zone.

With the arrangement of FIG. 3 oversized materials collecting on thescreen will naturally migrate to a catchment area at the end of thesieve and can be periodically removed (eg; with screen removal andreplacement) or preferably can be collected in a trap peripherally ofthe screen (ie; they migrate under the shaking of the screen [e.g. bysome eccentric mass (not shown) acting on the member 30] and/or witheffect of the flow through) from whence they can be removed. To enhancethis effect the sieve or screen 27 can slope slightly to trap 29 and thesieve carrying assembly 28 can be resiliently mounted relative to member30 reliant on rubber bushes 31.

1. A method of partitioning solids of a slurry three ways, said methodcomprising providing a housing having an inlet, a first outlet, and acollection zone, and, disposed therein, a sieve disposed below saidfirst inlet and said first outlet but above said collection zone,passing a slurry via said inlet into the housing across the sieve and,in part, out of said first outlet whilst at least some of the solids ofthe slurry fall onto and/or through the sieve, harvesting or using thesolids that have passed through said sieve and into said collectionzone, harvesting or disposing of those solids that have passed out ofsaid first outlet, wherein said housing includes a second outlet viawhich a removing of those solids collected on the sieve occurs.
 2. Amethod as claimed in claim 1 wherein the harvesting or using of thesolids that pass out of said second outlet or into said collection zoneis as a slurry.
 3. A method as claimed in claim 1 wherein the harvestingor disposal of the solids that pass out of said first outlet is as aslurry.
 4. A method as claimed in claim 1 wherein the harvesting orusing of the solids that pass through the sieve is by a slurry feedthereof from said collection zone or from said second outlet into apressure vessel from whence the solids may be expressed under the actionof water addition into such pressure vessel.
 5. A method of claim 1wherein said slurry to be partitioned includes solids for recycle use inan abrasive water jetting system.